osmosis questions?

Question

what osmotic regulatory challenges would a fish living in freshwater have versus a fish living in salt water?

also, when preparing sauerkraut, shredded cabbage, it is layered with coarse salt crystals. what affect would this have on the cabbages cells?

Answer 1

Freshwater and marine fish don't have challenges living in their environments because they have evolved physiological adaptions.

I'm not sure about the saurkraut question.

Answer 2

I am not a biologist, but I can think through your question.

Osmosis means to make something go from high concentration to low concentration. An imperfect, but visual analogy is if you have put ink in water and see how it dissolves.

Now if you think about it, the problem is not so much the osmosis from the outside to the inside. But the opposite way. The fish's blood should have more "stuff in it"; thus even though salt is more likely to get into the fish, there are plenty of other stuff that wants to get out.

Now, this is under the assumption that there IS a semipermeable membrane between the fish an its environment. Think if you have two compartments, osmosis would not happen between them if there was a piece of wood between them.

This begs the question, does the fish really have a semipermeable membrane? The answer is probably no. They have scales that are virtually impermeable.

So, aha! Fishes from the sea can avoid the issue entirely by having scales. But, let's also consider though, that the scales may be used also for defense/pressure. Not necessarily for osmosis.

So my conclusion is that fish scales may have been used for osmotic purposes as well... tada!

Answer 3

Freshwater fish must have a regulatory mechanism to keep out excess water. Salt water fish need to be able to absorb needed water for metabolic activities.

In high salinity, cabbage cells will partially dehydrate; thus they will have much less water content than normal.

Answer 4

The physiology of fishes living in different environments is different. Salt water fishes have a different osmotic potential. Osmosis is like diffusion but for water. water follows a gradient depending on the mediums osmotic potential or soakablity for it.